As the use of potable terminals, such as a smart phone, a tablet PC and a portable multimedia player (PDP), increases, a battery use time as a key to the use of the portable terminal along with performance of the portable terminal becomes the important issue. In other words, since the portable terminal cannot use a high-capacity battery due to its portability, a need to develop a technology of extending a battery use time increases.
In this regard, a Korea Patent Application Publication No. 10-2008-0111997 directed to device and method for power-controlling a portable terminal discloses a technology that when supply voltages of battery cells drop around the end of a discharge thereof and discharge currents from battery cells thus increase, connection of the battery cells is changed, thus a magnitude of the supply voltage increases, and thus a battery use time is extended.
The above-described prior art has an object to reduce the discharge currents from the battery cells, but it is problematic that an increase rate of battery use time is not much.